It is difficult to keep tight alignment between an object scene and laser rangefinders or laser designators while making adjustments such as moving a reticle during bore-sighting or weapon zeroing. For example, when range to a target is found using the laser rangefinder and the ballistic adjustment is made, for targets at longer ranges the vertical change for the ballistic path and the laser path diverge, resulting in the laser aiming point moving out of the sight field of view. If a range update is required, the sight must be mechanically re-set to bring the laser rangefinder back into the field of view.
There have been some attempts to integrate displays and laser rangefinders into rifle sights. One approach has been to mount the projected lasers and other devices separately, and/or to use a separate aperture for the laser rangefinder that is independent of the scene or reticle adjustment. However, if multiple apertures are used, the tolerances between the different systems must be added and make it difficult to maintain alignment at long ranges. Thus, this approach is complicated, and adds expensive mechanical structure that adds significantly to the cost and weight of the sight.